Meaning

adjective of surpassing excellence

adjective having or marked by unusual and impressive intelligence

adjective characterized by grandeur

originBorrowed from French brillant (late 17th century), present participle of the verb briller, from Italian brillare, possibly from Latin berillus, beryllus (“a beryl, gem, eyeglass”), from Ancient Greek βήρυλλος (bḗrullos, “beryl”). By surface analysis, French brill(er) + -i- + -ant.

Etymology from Wiktionary, CC BY-SA 3.0